(1) Field of the Invention
This invention relates to ethylene polymer/acrylonitrile polymer composites. More particularly, it relates to composites containing ethylene polymer polymerized onto the surface of a powdered or fibrous acrylonitrile polymer. It also relates to molded laminates made from ethylene polymer/acrylonitrile polymer fabric composites.
(2) Description of the Prior Art
The utility of organic polymers has been broadened in recent years to the degree that rigid polymers such as the nylons, ABS (acrylonitrile/butadiene/styrene) and polyacetal resins have begun to replace the more conventional metal, wood and ceramic materials. The lower cost of polyolefins such as polyethylene could make them candidates for a wider range of applications if certain properties such as heat deflection temperature, stiffness and hardness could be improved. Much research has been directed toward methods of improving these properties, mostly by filling polyolefins with finely-divided solids or fibrous fillers. The addition of fillers to polyolefins also serves to extend the use of polyolefins.
One such method which has led to composites of outstanding physical properties is described in German Patent Publication OLS No. 2,459,118. This publication describes homogeneous polyolefin/inorganic filler composites which comprise
(a) about 10-75% by weight of polyolefin having an inherent viscosity of at least about 4, and PA0 (B) about 25-90% by weight of finely-divided, inorganic filler compound having catalytically-active, transition metal compound interacted at its surface, in which the polyolefin is polymerized onto the surface of the filler in the presence of an organoaluminum compound. There is no mention of organic fillers in this publication.
One of the areas in which polyolefins have not been useful heretofore is in the area of reinforced polymer laminates. Such laminates have heretofore been prepared by working a prepolymer of syrup-to-paste consistency such as a polyester prepolymer into a layup composed of alternate layers of a reinforcing fabric such as fiberglass and the prepolymer, and further polymerizing the prepolymer by application to heat to form solid polymer. Since polyolefins do not have a prepolymer form they have not heretofore been suitable for this use. Accordingly, it would be desirable to provide a method of forming reinforced laiminates from inexpensive polyolefins.